1. Field of the Invention
This invention relates to a convenient copying machine and more particularly to a copying apparatus including a novel and convenient arrangement for developing with a liquid developer.
2. Description of the Prior Art
Copying machines may be of the liquid or the dry type. However, liquid development is superior to dry development in that it is higher in developing efficiency and can provide better image reproduction. On the other hand, liquid development is delicate in developing action and therefore, cumbersome procedures are required in construction of the portion in which the photosensitive medium is contacted by developing liquid, and maintenance of the toner density of the liquid and the circulation system therefor as well as periodic servicing or inspection is imperative.
Also, in the electrophotographic art using liquid developer to develop electrostatic latent images, there has heretofore been a developing device which comprises a developer containing portion for containing the developer therein and a developing portion for developing an object to be developed on a photosensitive medium or the like, the developer containing portion and the developing portion being individually constructed with a distance therebetween. In such device, the developing portion and the developer containing portion have been connected together by pipes or other connecting means so that the developer may be supplied from the containing portion to the developing portion and collected from the latter into the former portion. For the purposes of maintenance, repairs, inspection or the like, removal of the developer containing portion or the developing portion must be done either by excepting the connecting pipes or by simultaneously removing the two portions unstably connected by the thin pipes. In the first-named case, one end of the expected pipes would interfere with the removal of the portion to be removed, and developer would even leak through the disconnected pipe end to contaminate the device. In the latter case, simultaneous removal of the two portions connected by the thin pipes is a difficult task and, even if only one of the two portions is to be removed, both portions need be removed and this is wasteful and time-consuming.
For the detection of the density of the developing liquid in the developing device of the copying machine, use has been made of a photoelectric detector means which comprises a light source or lamp and a light-sensing element. However, such photoelectric detector means simply immersed in the developing liquid may often have its detecting function reduced by toner which tends to precipitate and solidify to stick to a wall portion corresponding to the optical path of the photoelectric detector means. In another prior art arrangement wherein the photoelectric detector means is disposed outside the developer container and supply of developing liquid is effected by pumping means, when the copying machine has been stopped from operating, developing liquid rarely stays in the detector means so that the surface of a transparent member accommodating therein the light source and light-sensing element is dried to permit residual toner to stick to said surface, thus rendering accurate detection of the density of the developing liquid impossible.